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PLENARY LECTURE - Simulation-aided geotechnical site investigation
No full textWith the advancement of computational geomechanics over the past decades, most of the activities typical of site characterization, such as in situ testing or sampling, can be realistically simulated using appropriate constitutive models and balance equations for geomaterials. These numerical simulations are not only informative of the processes that take place during testing but can be used to assess the reliability of current practice empirical interpretation techniques or even propose new interpretation techniques. In this paper, we present two numerical analyses of long-standing geotechnical problems in which new insights are gained by means of advanced numerical modelling. The first analysis corresponds to cone penetration testing in undrained, brittle geomaterials; we describe the effect of the constitutive parameters on cone metrics, and we propose a novel procedure to estimate the initial state parameter from CPTu based on a wide-ranging parametric analysis. The second analysis involves tube sampling in undrained geomaterials. A total stress analysis allows us to describe the kinematics of the soil during tube insertion and evaluate the effect of the tube geometry on the strain path of the problem. The analysis is then extended by considering a fully coupled hydromechanical formulation and a critical state constitutive model for cemented soils; by simulating conventional laboratory tests on the soil that has entered the tube we can quantify sampling disturbance in terms of geotechnical design parameters (e.g. undrained shear strength and yield stress). The possibilities offered by numerical modelling for site characterization are far from being fully exploited. It is envisaged that in the future site-specific numerical analyses will become available, enabling a more comprehensive understanding of the subsurface conditions
PLENARY LECTURE - Instrumental Dynamic Penetrometers for Geotechnical Characterization
No full textThe dynamic penetrometer is a common technique in geotechnical exploration and widely deployed throughout the world. However, while this technique has many advantages, it also has several disadvantages that can hinder its use and development. Indeed, it has evolved little, and its application has sometimes remained "rustic". But in recent years with the development of sensors, interpretation methods and digital technology, this technique has been adapted to improve the quality of measurement, the understanding of the phenomena occurring during the test and its exploitation. This article presents the recent developments and adaptations of this technique and their potential. After a brief review of the principle, history, and current limitations of the technique, we look at recent technological developments and the latest advances in terms of interpreting and using the test
Importance of Calibration Laboratories in In-situ Test Methods
Get PDFGeotechnical in-situ test methods provide valuable data for asset development, operation, and decommissioning. For confidence in test results, industry typically requires calibration and verification of in-situ test sensors to be conducted in a calibration laboratory. A calibration laboratory typically operates according to ISO/IEC 17025 (2017) ‘general requirements for the competence of testing and calibration laboratories’, or similar standard. This paper summarises observations from practice, with focus on the following challenges (1) evaluation of measurement uncertainty of key parameter values for which no standardised methods or verification materials are available, (2) validation of test methods with no backup from a formal standard published by a standardisation organisation and (3) field test site and interlaboratory comparisons within a competitive industry setting. Specific examples are presented for the (1) estimation of calibration uncertainty for sleeve friction of a subtraction-type cone penetrometer and (2) method validation for thermal conductivity of soil derived from in-situ heat flow measurements
Does CPT Reference Value Drift Really Inform CPT Correctness?
Get PDFThe two authors’ company (IGS) is an in situ testing and sampling contractor. Approximately 40% of the company’s business is cone penetration testing (CPT). The CPT cones they use are good quality commercial units supplied by the Dutch company Geomil, with qc capacities ranging from 3MPa to 100MPa. Both compression-type and subtraction-type cones are used. IGS undertakes their own in-house calibrations on all cones, using externally calibrated load cells, and a combination of dead weights and hydraulic load application. Calibration and adjustment is undertaken on every cone on an unusually frequent basis, explained in the paper, far more frequently than current standards or manufacturer recommendations require. At each calibration, the reference readings (sometimes known as baseline readings) of each cone’s tip qc, sleeve fs, and pore pressure U sensors are noted. And the slope of the applied-load/pressure-vs-cone-readout for each of these sensors (ie accuracy) is measured and adjusted to give as close as reasonably possible 100% accurate output. All of this is recorded for each cone. Thus the authors have a database of reference reading drift that can be compared to slope adjustments (ie calibration adjustments) that have been needed to achieve the desired cone accuracy. This paper graphically reports the data for tip and sleeve of eight typical CPT cones of the day-to-day types used by the company
Calibration Chamber Testing on Tailings for Interpretation of Partially Drained CPT
Get PDFThe Cone Penetration Test (CPT) is the primary site investigation tool in silt-rich tailings. The permeability and compressibility range of tailings often puts the standard CPT penetration rate in the partial drainage range where the tip resistance, pore water pressure, and sleeve friction become functions of not only the state, but also drainage conditions. This makes interpretation of the state parameter, which represents liquefaction susceptibility and residual strength of tailings particularly challenging. It is not clear whether existing CPT interpretation frameworks are capable of accounting for effects of partial drainage. Developing field correlations for interpreting partially drained CPT data in tailings is hampered by spatial variability and sampling disturbance. CPT tests were performed in a calibration chamber and in the field on a gold tailings material. Dissipation tests were performed, and the pore water pressures on the cone at the u2 position were monitored. The degree of partial drainage was estimated based on the coefficient of consolidation inferred from these dissipation tests. Similarities and differences of the calibration chamber and field CPTs were discussed
Landslide control in the excavation of a shallowly buried tunnel with a large front slope
No full textThe tunnel with a large front slope is a common type of entrance in mountain tunnels. Excavation of this type of tunnel disrupts the original balance of the slope, which can easily lead to landslides or collapses. It is therefore important to choose suitable support for early reinforcement. This paper presents a case study of landslide control during the tunnelling of a shallowly buried tunnel with a large front slope. Three types of pre-support, including anti-slide pile, pipe roof and surface grouting, were used to control the landslide. In addition, a three-dimensional analysis was carried out to investigate the reinforcing effect of single and multiple pre-supports on the landslide and tunnel structure. The results showed that the deformation of the landslide and tunnel structure at the end of the entrance was the greatest, that is, the most dangerous. In tunnel structures, the arch area was the most prone to instability, while the bottom area did not experience significant deformation. The horizontal displacement control effect of the landslide body was ranked from strong to weak as surface grouting, pipe roof, and anti-slide pile, while the vertical displacement control effect of the landslide was ranked from strong to weak as pipe roof, surface grouting, and anti-slide pile. The reinforcement effect when three types of pre-supports were applied simultaneously was basically equal to the sum of the reinforcement effects when each pre-support was applied separately. This is mainly due to the different reinforcement mechanisms and areas of the three pre-supports, resulting in better overall effects.
 
FINANÇAMENT DE LES POLÍTIQUES D’ACCÉS A L’HABITATGE SOCIAL DE LLOGUER
No full textConsiderem que l’habitatge és un pilar clau de l’Estat de Benestar com ho són l’educació, les pensions, la sanitat, o els serveis socials. La gran política habitacional és la que planteja abastir la demanda de parcs d’habitatge públics i socials mitjançant un finançament adient a les seves característiques i necessitats.
La comunicació pretén posar l’èmfasi en el finançament de la promoció d’habitatge social de lloguer, pedra angular per tal de proveir a la societat d’un parc que pugui abastar les necessitats sorgides de la darrera crisi financera (2088-2012) que ha suposat un punt d’inflexió en el mercat de l’habitatge, amb un protagonisme molt més accentuat de les transaccions del lloguer. Un canvi estructural produït pel fort augment de la precarietat laboral en determinats col·lectius socials, com ara les rendes baixes, la població estrangera, i els joves. Som del parer que és fonamental blindar el dret a l’habitatge per damunt de la seva consideració com un bé de mercat.
La comunicació farà un repàs de les circumstàncies que han conduit a Espanya i a Catalunya a la manca d’un parc d’habitatge social suficient (tant en propietat com de lloguer).
Segons la projecció de la creació de noves llars que fa l’INE i el PTSH (Pla territorial sectorial d’habitatge) és necessita la promoció d’habitatge social amb suport de l’Administració Pública a una mitjana de 15.000 habitatges/any, durant els propers 15 anys, una xifra molt allunyada de la producció dels darrers 10 anys.
Per tal d’assegurar el finançament de la promoció d’habitatge social de lloguer cal:
Continuar comptant amb finançament regular per part del Banc de Desenvolupament del Consell d'Europa (BDCE, CEB), que té com a objectiu millorar les condicions de vida i la cohesió social a Europa mitjançant el finançament de projectes d’alt impacte social, mitjançant la concessió de préstecs i garanties. I també poder accedir al finançament de projectes a llarg termini per part del Banc Europeu d’Inversions (BEI). La provisió d’aquest finançament és bo vehicular-la a través de l’Agència financera tant de l’Estat (ICO) com de la Generalitat de Catalunya (ICF).
I, com a novedós, replicar el «Pla d’Inversions per a una Europa Sostenible. Pla d’Inversions del Pacte Verd Europeu» => amb el «Pla d’Inversions per a una Europa Inclusiva. Pla d’Inversions del Pacte d’Habitatge Social Europeu» que garanteixi una vida digna a tota la ciutadania: accedir a un habitatge en condicions assequibles. I així, igual que hi ha el «bo verd europeu» o «BVEu» hi hagi també el «bo d’habitatge europeu» o «BHEu». La pretensió de la Comunicació és que entre tots els agents implicats es pugui aconseguir durant el nou mandat del Parlament Europeu, juntament amb el Consell, adoptar un REGLAMENT (UE) que repliqui el del 2023/2631 de 30.11.2023 sobre els “bons verds europeus”, en aquest cas sobre els “bons d’habitatge social europeus”
Utilizing BERT for the Detection of Depression in Social Media Messages
No full textDepression is a global mental health issue generalized by a decrease in mood and satisfaction. Treatments for individuals afflicted with depressive symptoms include prescribed medications that require diagnosis to acquire. The purpose of this investigation was to accurately assist psychiatrists in diagnosis procedures to prevent both false positive and false negative conclusions by utilizing machine learning on social media messages. This was done by training a machine learning algorithm which accurately predicted and detected depressive behaviors and communications. As social media messages encompass individual’s general communications among long periods of time with high consistency and frequency, I hypothesized that social media messages could be used as a method to both train an accurate and consistent machine learning model for the detection of depression. Social media dataset messages rely on self-reported diagnoses. Based on F1 accuracy normalization across machine learning HyperTuning, average accuracy indicated 97% [+/-0.5%] among a ~7600 sample dataset. Utilizing generalized sentimental analysis has shown less accurate results (~80%) but needs further research
Admissible values for the interaction term of the Tsai-Wu failure theory under plane stress and fitting of the failure envelope to test data
No full textThe Tsai-Wu failure criterion is widely used for orthotropic composite materials under plane stress due to its simplicity and low number of material constants. However, there is no consensus on how to find the interaction term. Based on general failure mode interaction assumptions, this paper provides closed form expressions to find the interaction term. In addition, the suitability of the Tsai-Wu’s failure criterion is narrowed to materials whose properties meet specific relationships. Last, it is shown how the Tsai-Wu failure envelope can be defined to pass through four biaxial stress states that best represent the actual testing conditions. All these findings conform an easy-to-apply methodology to define the Tsai-Wu failure envelope that best fits specific assumptions and test data
Performance of eco-composite sandwich panels manufactured by vacuum bagging infusion
No full textThe construction industry uses a complex combination of materials associated with a high carbon dioxide footprint. Therefore, several new building systems and solutions have emerged with higher sustainability and improved energy efficiency over their service lives, with the development of customizable lightweight sandwich structures, being one of the most promising strategies. The common processes for manufacturing fibre-reinforced polymer (FRP) composites, with large dimensions, are both hand layup-assisted vacuum bagging and vacuum bagging infusion. Besides, composite sandwich panels are traditionally composed by glass fibres and thermoset resins. However, basalt fibres can be an interesting substitute, since they are more sustainable, and have a higher performance. Despite the large amount of research work carried out on advanced composite sandwich panels, only a few studies were focused on the manufacturing of these structures based on basalt fibres assisted by vacuum infusion. Therefore, this work aims to design, manufacture and compare the mechanical, physical, thermal and environmental performance of these composite sandwich panels, comprising either glass or basalt fibres, which will be further applied in modular construction. The results revealed that it is feasible to produce composite sandwich panels through this method, and the most promising solution attained through this study is based on basalt fibres